Synthesis, Spectroscopic Characterization, and DFT Calculations of 1-(2,4-Dinitrophenyl)-3,5-Dimethylpyrazole
Fatou Dieng
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Mamadou Dieng
Laboratoire de Chimie Physique Organique et d’Analyses Environnementales, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal and Departement Physique et Chimie, Faculté des Sciences et Technologies de l’Education et de la Formation, Université Cheikh Anta Diop, Dakar, Sénégal.
Mouhamadou Sembene Boye
*
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal and Departement Physique et Chimie, Faculté des Sciences et Technologies de l’Education et de la Formation, Université Cheikh Anta Diop, Dakar, Sénégal.
Arona Ngom
Laboratoire de Chimie Physique Organique et d’Analyses Environnementales, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Adrienne Ndiolene
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Mouhamadou Birame Diop
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Momath Lo
Laboratoire de Chimie Physique Organique et d’Analyses Environnementales, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Modou Sarr
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Mohamed Lamine Sall
Laboratoire de Chimie Physique Organique et d’Analyses Environnementales, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
Aminata Diassé Sarr
Laboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
*Author to whom correspondence should be addressed.
Abstract
The attempted synthesis of a Schiff-base–type compound unexpectedly led to the formation of an organic product corresponding to an asymmetric dimer, resulting from a condensation reaction between 2,4-dinitrophenylhydrazine (C₆H₂N₄O₄) and acetylacetone (C₅H₈O₂) in methanol, in a 1:1 stoichiometric ratio. The compound crystallises in the monoclinic crystal system with space group P2₁/c and contains four independent units per unit cell (Z = 4). The unit cell parameters are: a = 20.4248(12), b = 7.7094(4), c = 16.7101(5), α = γ = 90°, and β = 113.745(7)°. In order to confirm the proposed structure, an experimental study was performed using infrared (IR), nuclear magnetic resonance (NMR), and UV–Visible spectroscopies, complemented by single-crystal X-ray diffraction. In addition, a theoretical investigation based on Density Functional Theory (DFT) was carried out to analyse Mulliken charges, vibrational assignments, and global reactivity descriptors of the compound. Calculations were performed using the B3LYP method with the B3LYP/6-311++G(d,p) and B3LYP/6-311G(d,p) basis sets. The calculated vibrational frequencies were employed to simulate the infrared spectra for both basis sets. Finally, the frontier molecular orbital energies (HOMO and LUMO), the energy gap, and the global reactivity parameters were determined in order to predict the chemical reactivity of the compound. Overall, the results highlight a strong correlation between experimental and theoretical data, emphasising the significance of electronic and structural interactions in the stability of the compound. Notably, the compound exhibits a calculated HOMO–LUMO energy gap of 3.625 eV (B3LYP/6-311++G(d,p)), indicative of good kinetic stability and moderate chemical reactivity.
Keywords: Pyrazole, 2,4-dinitrophenylhydrazine, acetylacetone, single-crystal X-ray diffraction, FT-IR spectroscopy, NMR spectroscopy, UV–Visible spectroscopy, density functional theory, frontier molecular orbitals, Mulliken atomic charges